The present invention relates to a method of laser writing multiple updatable 2-D bar codes on optical memory cards and labels which are readable with a photo-detector array such as a CCD array.
The commercial fields for linear optical data storage include optical memory cards, two-dimensional bar codes, and digital sound on motion picture films.
The PDF-417 (Portable Data File), two-dimensional bar code has become a widely accepted way of storing data on cards, documents, and packages. It is used to encode graphics, including fingerprints. It has begun to be used as a form of postage stamp printed by a laser printer connected to a personal computer following authorization over the Internet. The PDF-417 specification was disclosed in 1991. PDF-417 utilizes images with minimum dimensions of about 150 microns. An earlier, higher resolution form of two-dimensional bar code was disclosed in U.S. Pat. No. 4,634,850 entitled, xe2x80x9cQuad Density Optical Data Systems,xe2x80x9d assigned to Drexler Technology Corporation, which was filed Nov. 4, 1985, and issued Jan. 6, 1987. A closely related patent is U.S. Pat. No. 4,786,792 issued Nov. 22, 1988, which is also assigned to Drexler Technology Corporation. These two patents relate to reading a high-resolution form of two-dimensional bar codes with image dimensions of 3 to 35 microns compared with the 150-micron image dimension of PDF-417. Examples of patents directly related to the PDF-417 system are U.S. Pat. Nos. 5,243,655, 5,304,786, and 5,319,181 filed from 1990 to 1992 and issued 1993 and 1994, which are assigned to Symbol Technologies Inc.
Other 2-D bar code products, in addition to PDF-417, include Aztec, Code 16K and Code 49. When PDF-417 is referred to in this application, it is meant when applicable, to include other 2-D bar code products as well. A nine-page article entitled xe2x80x9cFundamentals of Scanning New 2-D Codes with CCD Area Imagersxe2x80x9d, has been published by Auto Image ID, Inc. of Cherry Hill, N.J., 08003.
Three patents have been assigned to Drexler Technology Corporation which involve the laser recording on reflective optical data storage medium using a microscopic laser beam of one to a few microns in diameter to create eye-visible images formed from pixels (picture elements), which in turn are formed from groups of 4, 9, or 16 closely-spaced laser-recorded microscopic spots. These pixels are used to create visual alpha-numeric characters or images, including portrait images of people. The three Drexler Technology patents are U.S. Pat. No. 4,680,459 entitled, xe2x80x9cUpdatable Micrographic Pocket Data Card,xe2x80x9d U.S. Pat. No. 4,814,594 entitled, xe2x80x9cUpdatable Micrographic Pocket Data Card,xe2x80x9d and U.S. Pat. No. 5,421,619 entitled, xe2x80x9cLaser Imaged Identification Card.xe2x80x9d
Methods and apparatus involving linear optical data storage of data on motion picture film are described in the following seven U.S. patents. In these cases the digital optical data represents motion picture digital sound. Two of those patents, assigned to Drexler Technology, are U.S. Pat. Nos. 4,503,135 and 4,603,099. Patents assigned to Sony Corporation in this field include U.S. Pat. Nos. 5,471,263, 5,523,996, 5,543,868, and 5,666,185. One of the relevant motion picture sound patents assigned to Dolby Laboratories is U.S. Pat. No. 5,710,752.
Another relevant patent is recently-issued U.S. Pat. No. 5,932,865 assigned to Drexler Technology Corporation, which is entitled, xe2x80x9cAnti-Counterfeit Validation Method for Electronic Cash Cards Employing an Optical Memory Stripe.xe2x80x9d Two sentences in the abstract point out the relevant features of this patent; namely, xe2x80x9cSuch counterfeiting can be inhibited by bonding an optical memory stripe to the smart card with pre-recorded or post-recorded validation data on the card. This optical validation data would be read with a photodetector array and could be transmitted to the recipient during funds transfer and/or used locally to control dispensing of cash.xe2x80x9d This patent explains the importance of laser recording data which are readable with CCD arrays, but does not disclose the method of the present invention.
Typical optical memory cards utilize a 35 mm or 16 mm wide, reflective optical memory recording stripe which stores about one to four megabytes of data when 2.5 micron spots and 12 micron track-to-track spacings are used. The reader/writer device sells for about $2,500, and read-only devices for those cards are also expensive because of the precision required to track the digital data on the optical card with a low power laser diode. Customers have requested an inexpensive, read-only device for the optical memory cards, and it is believed some customers would probably accept a somewhat lower data-storage-capacity card if that would lead to an inexpensive read-only device.
It is the object of the present invention to devise a method and apparatus for laser recording of a single or multiple two-dimensional bar code(s) readable with CCD or other photodetector arrays and with data storage capacities ranging from about 15 to more than 500 times greater than that of PDF-417 bar codes. Another object is to utilize data-pixel-based two-dimensional bar codes on cards or labels for authentication, validation, authorization, or identification involving Internet and Intranet E-Commerce transactions, documents, communications, and manufactured products. Another object of the invention is to devise a method and apparatus to make CCD-read data-pixel-based two-dimensional bar codes updatable. Another object is for an optical memory card to be utilized in reading and writing microscopic data spots that can be grouped into large data pixels to form single dimension bar codes known as 1-D bar codes. The 1-D bar code product types include Code 39, Code 93, Code 128, Code 11, Code B, Coda Bar, EAN, UPC, MSI, PostNet, Royal Mail (RM 45CC), and Telepen.
The above objectives have been met by a pre-formatted, laser-recordable optical memory stripe or patch being bonded to a plastic card, or to a label medium coated with an adhesive. The laser recording material should be of the DRAW (direct-read-after-writing) type where laser data is instantly recorded without a post processing operation. The pre-formatted data tracks on the optical memory stripe or patch would be separated by a distance of about 5 microns to 40 microns and preferably, to accommodate existing commercial equipment such spacing should be about 12 microns, which represents an ISO standard for optical memory cards. The 12 micron spacing would include a linear edge region 2 microns wide and a linear recordable region 10 microns and thus an edge-to-edge spacing of 12 microns.
The laser-recorded microscopic data spots are defined as in the range of between 0.6 microns to 3 microns in diameter but more typically for optical memory cards at about 2.5 microns in diameter. The number of microscopic data spots that could fit across a track width could be as small as two and as many as seventy, with about two to six being preferred.
Whereas read-only devices utilizing laser tracking of pre-formatted tracks are expensive, a read-only device using a linear CCD array to read multiple tracks encompassing large data pixels can be inexpensive under the right design conditions. To minimize data errors, at least two or three photosensitive detectors of the photodetector array should read each data pixel. The use of 7- to 10-micron size data spots with a CCD array would work technically but might not lead to the lowest price read-only device today, owing to the cost of the required CCD array. CCD arrays become lower in cost when the size of the data spots being read are greater than 10 microns, but data storage capacity of an optical memory card is reduced for larger data spots by the square of the data spot size. If the data pixels are used to form miniature versions of standard one-dimensional or two-dimensional bar codes are large enough they can be scanned and read with a laser beam and one or more single photodetector(s).
The objects of the invention are achieved by creating an array of uniform data spot pixels, or simply data pixels, whose linear size might be as small as seven microns or greater than 50 microns by use of properly arranged groups of spots, preferably about 2.5 microns in diameter. Smaller spots can be used, but then more of them would have to be utilized to create the large data pixels. Larger spots could be used, but laser diodes have limited output powers, and spreading the beam to larger diameters would reduce recording efficiency. The method involves the recording of a series of 2.5 micron spots in sequence without the normal 2.5 micron spacing between them so as to create a continuous data bar of lower reflectivity, for example, 25 microns long and 2.5 microns wide. For commercial optical memory cards, the recorded spots are recorded in the center of the 10-micron wide, highly reflective flat track defined by a 2-micron wide, low reflectivity border region along each edge of the 10-micron wide data track. Thus the center-to-center spacing between spots centered in adjacent tracks is 12 microns. Since the goal is to transform a 10 micron by 25 micron region of a track from high reflectivity to low reflectivity to create a data pixel, the first 2.5 micron by 25 micron bar may not necessarily be recorded in the center of the 10-micron track. Recording it anywhere in the track leaves room for a second, and probably a third, 2.5 micron by 25 micron bar to be recorded in the same track. Thus in that 25-micron long, 10-micron wide reflective track, 5 to 7.5 microns of width are taken up by the low reflectivity laser-recorded data bars. The remaining unrecorded track would remain at a high reflectivity, perhaps in the range of 40% to 50%. reflectivity, while the laser-recorded data bars might have a reflectivity of about 10%.
By this procedure, a lowered reflectivity region is created of about 12 microns in width and 25 microns in length. To create the desired 24 micron by 25 micron data pixel, the above procedure must be repeated with one adjacent track containing two to three similar low reflectivity data bars. One 24 micron by 25 micron data pixel is thus created by four to six laser-recorded data bars 2.5 microns wide and 25 microns long, distributed over two adjacent tracks with two to three of the low reflectivity data bars in each track. This lowered reflectivity 24 micron by 25 micron region is designated a data pixel and would represent a binary xe2x80x9cone,xe2x80x9d while a similar size, high reflectivity data pixel without any laser recorded data bars would represent a binary xe2x80x9czero.xe2x80x9d The objective would be for the contrast ratio between the reflectivity of a xe2x80x9conexe2x80x9d data pixel and the reflectivity of a xe2x80x9czeroxe2x80x9d data pixel to be in the range of about 1.5:1 to 2:1, which would be sufficient for data detection with low error rate.
The use of a large data pixel reduces the typical data capacity of four megabytes for an optical memory card with a 35 mm storage stripe on it. For example, a 24 micron by 25 micron data pixel would normally contain five data spots per track, and thus the two tracks would normally have contained ten data spots where now there is only one data pixel. Thus for the 24 by 25 micron pixel, the data pixel storage capacity of the same optical memory card would be reduced to about a factor of 10 to 400 kilobytes for a 35 mm -wide optical stripe and to about 180 kilobytes for a 16 mm-wide optical stripe.
The data storage capacity has been reduced. However, for a 16 mm stripe, it is 90 times greater than the two kilobytes stored on plastic cards using a PDF-417 patch and 22 times greater than the 8-kilobyte storage of a microchip smart card. The data storage capacity increases to about 1600 kilobytes for a 35 mm stripe and about 720 kilobytes for a 16 mm stripe if a data pixel size of 12.5 microns by 12 microns is used.
The method and apparatus for reading the data pixels from a data-pixel card or data-pixel label will involve either CCD arrays or other photodetector arrays. The photodetector array could be of the linear variety, in which case the card would have to be in motion when read. In the case of a two-dimensional photodetector array the card would not require motion but instead would be scanned electronically. The use of two-dimensional CCD arrays to read data from an optical memory is described in U.S. Pat. Nos. 4,745,484 and 4,864,630. The use of a linear photodetector array to read optical memory is described in U.S. Pat. No. 4,634,850.
A standard one or four-megabyte optical memory card can be used with a standard card reader/writer to create a data-pixel card. The desired data can be recorded on a card as 2.5 micron data spots. Then a software program would be loaded into a PC which controls the card reader/writer which would read the desired data on the card and in a step-by-step process translate the microscopic spot data into the data pixel format. That data can then be used to record the data on the same card or another card in the form of large data pixels that can be formed into groups or a series of 2-D or 1-D bar codes.
The use of the laser-created large data pixels in conjunction with a CCD array to read the pixels is estimated to reduce the cost of the read-only device by a factor of four from a laser-based, read-only device tracking 2.5 micron data spots. It also permits the read-only device to be portable for use, for example, in reading personally-carried medical records in an ambulance, or by military medics, or in the event of automobile accidents or other catastrophes. The use of the data pixels permits border crossing visa cards to be read in the field by inspectors, and for digital driver""s licenses to be checked for validity easily. A small, inexpensive, read-only device would open the optical memory card market to pay-per-use home T.V. and Internet services and to authorize purchases by welfare recipients in retail establishments.
Also, data-pixel-based two-dimensional bar codes on smart/optical cards can be used for authentication, validation, authorization, or identification involving Internet or Intranet E-Commerce transactions as explained in U.S. Pat. No. 5,932,865, assigned to Drexler Technology Corporation. The data-pixel-based information may be in the form of a portable data file database of medical, financial information or software wherein some of which read by the photodetector array is transferred to the microprocessor chip or to a personal computer or network such as the Internet with which said microprocessor chip is interacting for utilization of said data-pixel-based information. Said data-pixel-based information might, for example, include the card holders demographics, a card serial number, date of card issuance, geographical location of the issuer, types of purchases permitted or not permitted, date of expiration, maximum dollar value of individual purchases or purchases over a period of time or any other data related to authentication, validation, authorizations and identification that raises the security of E-Commerce transactions.
Another object of the invention is to devise a method and system to make CCD-read data-pixel-based two-dimensional bar codes updatable. This is accomplished by utilizing a laser-recordable optical memory card that uses a DRAW (direct-read-after-write) laser recording material. A DRAW material records immediately after laser beam exposure and does not require a processing operation like photographic film. The optical memory card is preferably formatted to facilitate the recording of the microscopic data spots precisely in the required locations, which will be grouped into data pixels. By recording of the initial amount of data which does not fill the data capacity of the card, at a later time new data may be added. As indicated previously, a 16 mm optical stripe on a commercially-available optical memory card using 24 by 25 micron data pixels would store 180 kilobytes of data, representing about 90 single-spaced typewritten pages. Thus, for example, if the equivalent of five typewritten pages were recorded for each data entry, a total of 18 such data entries could be made. If a miniature two kilobyte PDF-417 format is utilized the 180 kilobyte data capacity would permit 90 such miniature PDF-417 patterns to be recorded over a period of time.
Another object is for an optical memory card to be utilized in reading and writing microscopic data spots during some time periods and writing and reading large data pixels during other time periods. This is accomplished by using a laser-recordable, pre-formatted optical memory card which uses a DRAW (direct-read-after-write) material. The pre-formatting of recording tracks and separator bands can be accomplished by molding, pressing, or by the methods described in U.S. Pat. Nos. 4,542,288 and 4,304,848, assigned to Drexler Technology Corporation. The DRAW material is important, since it requires no post-processing after laser recording and therefore permits hundreds and thousands of data entries over months or years. The track pre-formatting on the optical memory card is desirable since it facilitates precise location of the laser-written microscopic data spots so they can later be precisely aligned into groups of data spots that create the required large data pixels. The standard for commercial optical memory cards is to record the microscopic spots on the tracks at the lower end of the optical memory stripe first. Thus to accommodate writing and reading both microscopic data spots and the large data pixels, the latter should be recorded on the upper tracks. By this means, a 35 mm optical stripe using 2.5 micron data spots and 24 by 25 micron data pixels could record and store, for example, about two megabytes of microscopic data spots and about 200 kilobytes of data pixels.
When an optical memory card is subject to severe environmental conditions or misuse such as scratching, high temperature, moisture, chemical or ultraviolet light exposure, particularly over extended periods of time, some of the microscopic data spots can be lost. Error detection and correction (EDAC) systems are usually used to compensate for such situations. Also, additional microscopic spot data can be recorded redundantly on the card as a backup to the primary data in the event that critical data is lost. An even more secure approach to the problem is to record some of the critical data redundantly in the form of large data pixels on the same card. Thus if the primary critical data is lost, the large data pixels can be used for recovery.